Current wireless remote control units for consumer electronic equipment, such as television receivers, video cassette recorders, and cable or satellite receiver boxes, operate by transmitting an infrared (IR) light signal, representing a coded signal modulated on a modulating signal, from the remote control unit to the consumer electronic equipment. This modulated IR light signal is received by an IR receiver in the consumer electronic equipment, demodulated, decoded, and the appropriate action taken. IR remote control units are line-of-sight devices, meaning that any consumer electronic equipment which is in a shadow with respect to the IR light generated by the remote control unit will not be able to receive the IR light signal and respond to the command. In addition, IR remote control units have a limited operational range, which is sufficient for use within a room, but not sufficient for use between rooms.
Currently, however, consumer electronic equipment is being placed inside of pieces of furniture, such as home entertainment units, behind solid doors. For example, a television, cable box, satellite receiver, etc., may be placed in a home entertainment unit in such a manner that, though the television receiver is visible to the viewer, the cable box, satellite receiver and VCR are placed behind solid doors. In addition, consumer electronic equipment is being distributed among different rooms in a home. For example, a satellite receiver might be located next to one television receiver in a family room, but may also coupled to a second television receiver in a bedroom. The IR light generated by remote control units cannot penetrate through solid doors or pass from room to room, so the hidden or remotely located equipment may not be controlled.
To provide the capability of controlling consumer electronic equipment within cabinets or in different rooms of a home, IR repeaters have been developed. An IR repeater includes an IR receiver section located where it can receive the coded modulated IR signal generated by the remote control unit. For example, it may be located on the outside of an entertainment unit or in the room in which the remote control unit is being used. The IR receiver section is connected to an IR transmitter section located where the consumer electronic equipment which is to be controlled can receive its signal. For example, it is located inside of the entertainment unit or in the room in which the consumer electronic equipment is located. The IR transmitter section includes an IR light emitter which is placed so that the emitted IR light impinges on the IR receiver in the consumer electronic equipment to be controlled. More specifically, the IR light emitter is usually placed directly adjacent to the IR receiver in the consumer electronic equipment. The IR receiver section of the IR repeater detects the coded IR light signals produced by the remote control unit and transmits them to the IR transmitter section, usually via a wire. The IR transmitter section generates an IR light signal which is identical to the IR light signal received by the IR receiver section. The consumer electronic equipment receives this IR light signal from the IR transmitter section, and performs the desired function.
Different manufacturers of consumer electronic equipment use different modulating frequencies for modulating the coded control signal onto the IR light signal. In order for IR repeaters to work with the respective manufacturers' modulation frequencies, IR repeaters use an IR detector in the IR receiver section which has a relatively wideband frequency response characteristic. That is, it will detect modulated IR light signals for which the modulating frequency can vary over a relatively wide range of frequencies. For example, IR repeaters can generally detect IR light signals which are modulated at any modulating frequency from about 20 kilohertz (kHz) to 100 kHz. Any modulated IR signal in this frequency range may be detected by the IR receiver, and when detected, an IR signal mimicking the received signal is generated at the IR transmitter.
Recently fluorescent lights having electronic ballast, termed compact fluorescent lights (CFLs), have been developed as a replacement for incandescent lights. CFLs use less energy than incandescent lights, and have become popular for that reason. However, CFLs produce IR light which has characteristics similar to those of the coded modulated IR light signals produced by remote control units. That is, the electronic ballast in a CFL causes the fluorescent tube to produce IR light signals which appear to be modulated by a modulating frequency in the range of 20 to 100 kHz, and specifically by a frequency of about 56 kHz. In addition, the IR light produced by CFLs has an intensity far greater than that produced by remote control units. Thus, the IR light produced by a CFL completely overpowers the coded modulated IR light signal produced by a remote control unit. Because current IR repeaters mimic the IR signal received by its receiving section, any interference from nearby CFLs picked up by the IR repeater is also mimicked in the IR light signal produced by the IR repeater. It has been found that, in the presence of CFLs, IR repeaters have seriously degraded performance or even become completely inoperative.
IR detectors have been developed which are resistant to interference caused by CFLs. These detectors can receive an IR light signal representing a coded modulated control signal from a remote control unit in the presence of interfering IR light from a CFL and, and in a known manner, cancel the interference from the CFL. The coded modulated IR light signal from the remote control unit is then demodulated, and such an IR detector produces an electrical signal representing the coded control signal.
An IR repeater which can operate with remote control units from many manufacturers, and which can operate reliably in the presence of CFLs is desirable.